21755579 has 2 divisors, whose sum is σ = 21755580. Its totient is φ = 21755578.

The previous prime is 21755527. The next prime is 21755581. The reversal of 21755579 is 97555712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21755579 - 2¹⁶ = 21690043 is a prime.

Together with 21755581, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21755509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10877789 + 10877790.

It is an arithmetic number, because the mean of its divisors is an integer number (10877790).

Almost surely, 2^21755579 is an apocalyptic number.

21755579 is a deficient number, since it is larger than the sum of its proper divisors (1).

21755579 is an equidigital number, since it uses as much as digits as its factorization.

21755579 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 110250, while the sum is 41.

The square root of 21755579 is about 4664.2876197765. The cubic root of 21755579 is about 279.1623734198.

The spelling of 21755579 in words is "twenty-one million, seven hundred fifty-five thousand, five hundred seventy-nine".